Re: question about readonly instances

On 05/18/11 11:39 PM, Szymon Guz wrote:
>
> thanks for the answer. It is not a problem to have 3 oracle instances,
> in fact there will be hundreds of them probably, but could also be
> hundreds of Postgres instances :)

do you have any idea how EXPENSIVE 100s of Oracle RAC nodes are annually?

to share block storage between cluster nodes requires a cluster-aware
file system, as conventional file systems do not expect the disk files
to change behind their back.       these cluster-aware file systems have
a bunch of overhead in maintaining cache coherency between nodes, and such.

as far as I know, postgres can not be run on a read only file system,
further its shared_buffer caches couldn't possibly be aware of other
nodes modifying blocks that happen to be cached.